Adding support for this would require the addition of a _visit_AnnAssign node in the SyntacticParser.
I see two possible ways to manage the addition of this:

1. Add a new type to handle this. E.g an AnnotatedPyccelSymbol which inherits from PyccelSymbol
2. Create the Variable directly in the syntactic stage. This blurs the lines between the syntactic and semantic stage which makes it somewhat dangerous but it avoids unnecessary operations

Apart from the addition of a "Final" ("const") annotation, can you explain what this would add that the user couldn't achieve in pure Python? E.g:

@stack_array('z')
def f():
    x = 0
    y = np.int32(0)
    z = np.zeros((3,4))

I am generally not a fan of handling things in annotations which can be done in pure Python as it leads to the generated code behaving differently to the original Python code. As a result even if we were to support syntax such as:

y: "int32" = 0

I would expect it to raise a warning as a minimum to show that the results may not be as expected after testing in Python